This invention relates generally to molded bicycle components, including wheel designs, frames, and the like which join two halves together in order to form a single assembly. Specifically, the invention focuses upon bicycle component assembles which are efficient to manufacture and assemble, and yet which also have structural integrity similar to that of traditional bicycle components such as bicycle frames, handle bar designs, and wheel designs (including spoke designs) which are molded from multiple pieces and bonded into one assembly.
Regarding the wheel aspect, obviously, the wheel has been around for some time; it may even be considered the most fundamental invention of mankind. In spite of this history, the wheel is still the subject of continued improvement. These improvements are not merely efforts to "reinvent the wheel", they are actually incremental improvements which specifically adapt the wheel to different applications and make it more efficient for the end consumer. One of these fields, that of application to bicycles has also been known for years. This field is perhaps the one which is most subject to efforts at improved efficiency, be it in use, manufacture, or otherwise. Such improvements relate to the adaptations of new understandings and technologies in a manner which allows more efficient manufacture and utilization of such a well known item.
One of the more recent technologies which has been adapted for bicycle wheel applications is the technology of molding wheels. Improvements in this area have been fundamentally motivated by a pervasive desire to improve the efficiency with which such bicycle wheels are manufactured and yet maintain light weight.
The traditional bicycle wheel design involves a metal hub portion and a metal rim portion which are connected through numerous spokes. These spokes are usually each hand assembled and adjusted to achieve a perfectly circular and axially true wheel. The labor intense nature of such traditional spoke designs is one aspect which has great impact upon the cost of bicycle wheels. Obviously, by creating a design which is molded this significant cost impact can be avoided.
In spite of the rather obvious advantage of applying molding technology to this field, the technical challenges incidental to producing a molded wheel design have greatly limited the commercial acceptance of molded bicycle wheel designs in general. One of these challenges is the need to maintain light weight and yet strong structure. On the one hand, molded designs with solid spokes require structure to be located near the central axis, such as with an I-beam type cross section. This can limit the design characteristics. By analogy to I-beam construction, it can be more efficient to move structure off the axis, but this does not lend itself to the most simple molding processes. On the other hand, molding is more challenging for hollow items. Surprisingly, these and other technological hurdles have caused structural challenges for the field of bicycle wheels as its applications are actually one of the more demanding. Perhaps paradoxically, the challenges of applying molding technology have even lead toward increased expense for some designs.
Structurally, molded wheel designs have been faced with the challenge of allowing for two-part designs which can be joined together in a fashion that can withstand the significant stresses of such applications. In U.S. Pat. No. 4,344,655 to Pellegrino, a two-part molded wheel was disclosed in which the adjoining halves are held together through barbed designs which are molded as an integral part of each wheel half. While such a technique for joining the halves might work in low-stress applications such as the children's design as shown in that patent, singular fastening devices such as the barbs have an undesirable incident of concentrating stresses when the wheel is in use. Since the materials frequently used in molding items are not preferably materials which are particularly strong, this concentration of stresses has to some extent limited applications to items such as children's vehicles and the like.
Since these structural challenges are well known, several incremental improvements in more demanding applications such as the bicycle or motorcycle wheel have, of course, been proposed. In U.S. Pat. No. 4,527,839 to Fujitaka, it was proposed that a molded wheel be designed so as to be joined together through the use of both bonding and external fasteners. While for some designs such a technique might actually achieve sufficient structural integrity, obviously the assembly required for such designs degrades the efficiency which is a supposed hallmark of molded wheel designs in the first place. In addition, through its combination of bonding and fastening in order to join the two halves, the Fujitaka reference teaches away from the direction of merely bonding alone to join the two halves. Another challenge to joining wheel halves together was addressed in part in U.S. Pat. No. 3,695,728 to Haussels. In that patent, it was disclosed that the stresses near the center of the rim portion of the wheel are particularly acute. In order to deal with such stresses, the Haussels disclosure--again eschewing a bonded design--suggested placement of barb fasteners off the central plane to reduce forces. Among other aspects, this design represents not only a direction away from that taken by the present invention, but it is also an example of the seemingly narrow incremental improvements which are considered important when applied to such an invention which is as basic as the wheel.
Perhaps an even more extreme example of the challenging nature of joining two wheel halves together is demonstrated by a molded wheel design entitled "SPIN" by Innovations and Composites, Inc. This design (characterized by its inventors as "reinventing the wheel") goes to great lengths to avoid the two-part molded concept. Instead, it disclosed a single-piece molded design in which the hollow wheel is created through use of a lost core molding process, a process in which the core is melted out of the product after it has been molded. Although such a design does overcome the challenge of properly joining two or more parts together, it fails to achieve the most important goal of manufacturing efficiency. In fact the process is so expensive that the end wheel is significantly more expensive than traditional, albeit inefficient, spoke designs. Obviously, this direction does not achieve the low cost manufacturing efficiencies which are considered to be the hallmark of many molded wheel designs.
Regarding the bicycle frame aspect, some efforts have been made to functionally prepare and manufacture a molded bicycle frame. An example is U.S. Pat. No. 5,456,481 to Allsop. It shows two molded halves which may be joined. Little discussion is made of how to actually accomplish the joining of such pieces. The present invention discloses a novel method and system for securing a stable and strong shear bond joint, in addition to other features. Such a joint may be applicable in a variety of places throughout the bicycle components.
As the prior efforts demonstrate, although molded wheel designs have been known for over twenty years, and although there has long been an unsatisfied need for a satisfactory molded wheel design, until the present invention, such a design has not existed. A similar position may be taken for the other components, such as bicycle frames. For years, those skilled in the art have sought a molded wheel design which has been sufficiently easy and inexpensive to manufacture and assemble and which was also capable of satisfying the demanding structural needs of applications such as the bicycle field. Perhaps surprising in this regard is the fact that while the present invention merely implements arts which have long been available, until the present invention, those skilled in the art have not recognized the fact these could be implemented in a manner which would achieve these long felt needs. This was perhaps due to several factors. First, the attempts by those skilled in the art were directed away from designing the bond and wheel in a manner which was structurally appropriate. In some regards, they simply seemed to accept that bonding alone would not represent an adequate approach and may have even failed to understand that the problem lay in properly designing the wheel, not in applying different technologies. This may even have been fostered by the directions and teachings taken by some (such as those involved with the references discussed above) which were away from the directions taken in the present invention.